1. Field of the Invention
This invention relates to a method and apparatus for determining the effectiveness of a sterilization procedure, and more particularly to a biological sterility indicator providing a permanent visual record of the degree of effectiveness of the sterilization procedure.
2. Description of Prior Art
Surgical devices such as sutures, catheters, gloves, bandages, and the like are generally sterilized by the manufacturer so they are ready for use when delivered to the hospital. Sterilizing media such as steam, dry heat, sterilizing gases and radiation have been successfully employed. Problems have arisen, however, in determining the completeness or efficacy of sterilization procedures. It is highly desirable that means be provided whereby the efficacy of a sterilization cycle may be determined quickly and reliably, and without undue laboratory manipulations.
Heretofore, in one known method of sterilization testing, a source of live microbial spores contained on a piece of absorbent paper was placed in a sterilization chamber along with the objects to be sterilized. Upon completion of sterilization, the absorbent paper was removed and placed in a culture medium and the latter transferred to an incubator to develop the microorganisms in the culture. After several days, the culture medium was examined and tested to determine if any of the organisms survived the sterilization. This method not only required a high degree of skill and care in aseptic handling and evaluation of the culture medium, but also several days were required to develop the culture to the extent that a determination of spore survival could be made. Moreover, once the test was completed, the cultures were discarded and no record other than the observations of the analyst remained for future reference.
In most instances, the sterility test utilized a particular microorganism and concentration which was required to be completely killed in order for the sterilization cycle to be acceptable. More recently, Kereluk U.S. Pat. No. 3,711,378 proposed a system wherein a plurality of test strips, each containing different spore populations, were subjected to the sterilization cycle. After sterilization, the strips were removed and incubated in a culture medium to promote the growth of any surviving spores. The effectiveness of the sterilization cycle was determined according to the spore strip containing the highest population which was determined to be completely sterile after the sterilization cycle. Although this represented an improvement over the single test systems of the prior art, it nevertheless required multiple culture media and vessels and extended time to develop the culture medium after the sterilization cycle, and further required subjective evaluation by the analyst with no independent permanent record of the effectiveness of the sterilization being provided for future reference.
It is accordingly an object of the present invention to avoid and overcome the foregoing and other difficulties of the prior art practices.
It is a further object of this invention to provide a single sterility test strip which will indicate the degree of effectiveness of a sterilization cycle in terms of maximum microorganism concentrations killed by the cycle.
It is another object of this invention to provide a method and apparatus for providing a permanent visible record of the effectiveness of a sterilization cycle.
These and other objects of the present invention will be apparent from the ensuing description and claims.